This application relates to a refrigerant cycle that operates in a transcritical mode, such that there is freedom in the selection of discharge pressure. An optimum discharge pressure is identified based upon system conditions to maximize efficiency.
Refrigerant cycles are utilized to provide heating or cooling in a variety of applications. Generally, a compressor compresses a refrigerant and delivers that refrigerant to a first heat exchanger, at which heat is given off to another fluid. From this first heat exchanger, the refrigerant passes to an expansion device that expands the refrigerant. The refrigerant then passes to a second heat exchanger, where the refrigerant takes in heat from another fluid. The two heat exchangers often include one indoors and one outdoors. The refrigerant cycle is used to provide heating or cooling for a fluid at one of the heat exchangers.
While refrigerant cycles are often utilized to provide heating, ventilation or air conditioning (HVAC), there are other applications. In one non-HVAC application, a refrigerant cycle is utilized to heat hot water for sanitary water uses, such as a faucet, shower, etc. The present invention extends to both HVAC applications and other non-HVAC applications.
In one modern refrigerant system, the refrigerant moves above the critical point of a pressure enthalpy curve. Once above this point, the refrigerant cycle designer has more control over refrigerant operating pressures. In a standard cycle, there is less control over pressures, and a system design typically dictates operational pressure.
Various refrigerant cycles control pressure in transcritical systems. However, these controls have typically been for safety, such as to prevent over-pressurization. The prior art does not achieve the most efficient operation based upon this control.